1. Field of the Invention
The present invention relates to a substrate-bonding process method by using multilayer structure, and more particular, to a method for manufacturing Ni/In/Sn/Cu multilayer structure, in which the Ni/In/Sn/Cu multilayer structure made by the manufacturing method performs good wettability, ductility, creep resistance, and fatigue resistance, so that the Ni/In/Sn/Cu multilayer structure can be an alternative solder for replacing the traditional high-temperature Pb solder and being applied in the package process of 3D IC.
2. Description of the Prior Art
With the evolution of the times, the electronic package technology has been further developed due to the light and thin requirements on electronic products demanded by people. Integrated circuit (IC) is the base of the electronic product, and the IC chip design is developed and tended toward high pin number and multifunction, wherein flip chip technology is an alternative package technology for replacing the traditional bonding technology and used for packaging the high-pin number IC chip. Moreover, for filling large quantities of electronic components into a limited space, the package technology is further developed and tended toward system integrated stage, such as system in package (SiP); for this reason, 3D IC package technology becomes an important issue gradually.
Tin-lead is a conventional solder used in the bonding process of semiconductor devices; however, resulting from the increase of environmental awareness, the production of the electronic products including Pb has been forbidden according to the passed laws in some advanced countries, such as European Union, United States and Japan. Accordingly, in order to replace the tin-lead solder, industries then start to develop others alternative binary alloy solder. Please refer to FIG. 1, there is shown a schematic manufacturing process diagram of a semiconductor package substrate having a pre-solder structure. As shown in FIG. 1, the conventional semiconductor package substrate 2 having the pre-solder structure consists of a package substrate 3, an organic insulating protective layer 33, a conductive film 35, and a solder 38, wherein the a plurality of electrical connection pads 32 are formed on the surface of the package substrate 3. The organic insulating protective layer 33 is also formed on the surface of the package substrate 3, and the electrical connection pads 32 are exposed out of the surface of organic insulating protective layer 33 through thickness thinning process. The conductive film 35 and a resistor layer are sequentially formed on the surface of the package substrate 3, wherein the resistor layer has a plurality of openings. The conductive film 35 and the solder 38 is deposited on the electrical connection pads 32 by electroplating and exposed out via the openings of the resistor layer.
The solder 38 formed on the electrical connection pads 32 by way of electroplating deposition can be lead, tin, silver, copper, bismuth, antimony, zinc, nickel, zirconium, magnesium, indium, tellurium, gallium, or an alloy made of any two or above two elements. In addition, the solder 38 formed on the electrical connection pads 32 can be conductive post form, used for being electrically connected to the electrode pads 52 of the flip-chip semiconductor chip 51. Besides, there has a plurality of metal bumps 53 formed on the electrode pads 52 of the semiconductor chip 51. In the semiconductor chip 51, the electrode pads 52 are made of copper, and the metal bumps 53 can be a solder bumps, gold bumps, copper bumps, or copper posts covered with solder caps.
Inheriting to above descriptions, because the main bonding material used in the manufacturing process of the semiconductor package substrate having pre-solder structure is copper posts covered with solder caps, only Sn/Cu binary alloy would be produced at the bonding interface. Moreover, the poor wettability, poor ductility and high bonding temperature of the Sn/Cu binary alloy easily cause the damage of circuit board.
Thus, in view of the conventional semiconductor package substrate having pre-solder structure and the manufacturing method thereof still have shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a method for manufacturing Ni/In/Sn/Cu multilayer structure; in which the Ni/In/Sn/Cu multilayer structure made by the manufacturing method performs good wettability, ductility, creep resistance, and fatigue resistance, so that the Ni/In/Sn/Cu multilayer structure can be an alternative solder for replacing the traditional high-temperature Pb solder and being applied in the package process of 3D IC.